FXR agonists for MASH therapy: Lessons and perspectives from obeticholic acid.

Nonalcoholic fatty liver disease, also called metabolic dysfunction-associated steatotic liver disease, is the most common liver disease worldwide and has no approved pharmacotherapy. Due to its beneficial effects on metabolic regulation, inflammation suppression, cell death prevention, and fibrogenesis inhibition, farnesoid X receptor (FXR) is widely accepted as a promising therapeutic target for nonalcoholic steatosis (NASH) or called metabolic dysfunction-associated steatohepatitis (MASH). Many FXR agonists have been developed for NASH/MASH therapy. Obeticholic acid (OCA) is the pioneering frontrunner FXR agonist and the first demonstrating success in clinical trials. Unfortunately, OCA did not receive regulatory approval as a NASH pharmacotherapy because its moderate benefits did not outweigh its safety risks, which may cast a shadow over FXR-based drug development for NASH/MASH. This review summarizes the milestones in the development of OCA for NASH/MASH and discuss its limitations, including moderate hepatoprotection and the undesirable side effects of dyslipidemia, pruritus, cholelithiasis, and liver toxicity risk, in depth. More importantly, we provide perspectives on FXR-based therapy for NASH/MASH, hoping to support a successful bench-to-clinic transition.

Obeticholic acid-a new therapy in PBC and NASH.

INTRODUCTION: Obeticholic acid (OCA) is a semi-synthetic hydrophobic bile acid (BA) analogue that is highly selective agonist of farnesoid X receptor (FXR), a key nuclear BA receptor, which induces expression of gut-derived hormones, in particular fibroblast growth factor 19. The resulting beneficial effects of OCA on glucose and lipid metabolism and particularly hepatic inflammation make it a candidate for the treatment of a variety of conditions including primary biliary cholangitis (PBC) and nonalcoholic steatohepatitis (NASH). SOURCES OF DATA: In PBC patients who have not initially responded to ursodeoxycholic acid, OCA has been shown in double-blind controlled clinical trials to significantly reduce serum alkaline phosphatase. To date, OCA is the only therapy licensed by the FDA, EMA and endorsed by NICE as second line therapy for PBC.No medications are currently approved in Europe or the USA for the treatment of NASH.In recent clinical trials, OCA has been shown encouraging results by improving liver blood tests and reducing liver fibrosis with no worsening of NASH. AREAS OF AGREEMENT: OCA is the established second line therapy for PBC in those patients who fail to adequately respond to ursodeoxycholic acid. AREAS OF CONTROVERSY: The main side effects of OCA treatment in both PBC and NASH is that of dose-dependent pruritis which can lead to treatment discontinuation in ~1-10% of patients. In addition, OCA-treated patients may also exhibit (reversible) alterations in serum lipid levels; most notably a small decrease in high density lipoprotein cholesterol. It is not yet known whether these changes carry a long-term cardiovascular risk in NASH.In addition, the relatively high cost of OCA may limit its use in cash-limited health systems. GROWING POINTS: Additional clinical trials are in progress to ascertain the long-term effects of OCA on survival in PBC and NASH. AREAS TIMELY FOR DEVELOPING RESEARCH: New FXR agonists with a lower rate of side effects are being developed and trialed. Combination therapy with other agents may offer increased efficacy.

Emerging New Diagnostic Modalities and Therapies of Nonalcoholic Fatty Liver Disease.

PURPOSE OF REVIEW: Nonalcoholic fatty liver disease (NAFLD) has emerged as the leading cause of chronic liver disease in both adults and children. In this article, we review recent developments in the screening, diagnosis, and treatment of pediatric NAFLD. RECENT FINDINGS: Although alanine aminotransferase (ALT) remains the best screening test for NAFLD in children, and liver biopsy is still required for the diagnosis of nonalcoholic steatohepatitis (NASH), other noninvasive biomarker/imaging studies (MRI-PDFF and VCTE) have emerged as diagnostic methods for pediatric NAFLD. Two large clinical therapeutic trials testing vitamin E, metformin, and cysteamine in pediatric NAFLD yielded mostly inconclusive results. Bariatric surgery has begun to be used in adolescents with severe obesity. An adult phase 2 study using obeticholic acid (OCA) to treat NASH patients with fibrosis showed some positive results. As we continue to await the first FDA-approved therapeutic agent for NASH, lifestyle change remains the main modality of treatment. Newer diagnostic and treatment modalities for pediatric NAFLD continue to be in development under FDA guidance.

Microbiota metabolized Bile Acids accelerate Gastroesophageal Adenocarcinoma via FXR inhibition.

Background: The incidence of Barrett esophagus (BE) and Gastroesophageal Adenocarcinoma (GEAC) correlates with obesity and a diet rich in fat. Bile acids (BA) support fat digestion and undergo microbial metabolization in the gut. The farnesoid X receptor (FXR) is an important modulator of the BA homeostasis. The capacity of inhibiting cancer-related processes when activated, make FXR an appealing therapeutic target. In this work, we assess the role of diet on the microbiota-BA axis and evaluate the role of FXR in disease progression. Results: Here we show that high fat diet (HFD) accelerated tumorigenesis in L2-IL1B mice (BE- and GEAC- mouse model) while increasing BA levels and enriching gut microbiota that convert primary to secondary BA. While upregulated in BE, expression of FXR was downregulated in GEAC in mice and humans. In L2-IL1B mice, FXR knockout enhanced the dysplastic phenotype and increased Lgr5 progenitor cell numbers. Treatment of murine organoids and L2-IL1B mice with the FXR agonist obeticholic acid (OCA) deacelerated GEAC progression. Conclusion: We provide a novel concept of GEAC carcinogenesis being accelerated via the diet-microbiome-metabolome axis and FXR inhibition on progenitor cells. Further, FXR activation protected with OCA ameliorated the phenotype in vitro and in vivo, suggesting that FXR agonists have potential as differentiation therapy in GEAC prevention.

Computational study of novel natural agonists targeting farnesoid X receptor.

The farnesoid X receptor (FXR) is a crucial therapeutic target for treating non-alcoholic steatohepatitis (NASH). Although obeticholic acid (OCA) as a FXR agonist presents good efficacy, the safety data such as severe pruritus should be carefully considered. To discover new medications, we screen and choose the optimal compounds from ZINC15 database that may agonistically interact with FXR. We utilized the DS19 software to assist us in conducting the computer-aided structure based virtual screening to discover potential FXR agonists. After LibDock scores were determined by screening, their absorption, distribution, metabolism, excretion and toxicity predictions were examined. To determine the binding affinity between the chosen drugs and FXR, molecule docking was utilized. Molecular dynamics simulation was utilized to evaluate the stabilization of the ligand-FXR complex in its native environment. Higher binding affinity and stability with FXR were observed for ZINC000013374322 and ZINC000006036327, as two novel natural compounds, with lower rodent carcinogenicity, Ames mutagenicity, no hepatotoxicity and non-inhibitors of CYP2D6. They could stably exist in the environment, possess favorable potential energy and exert pharmacological effects at lower doses. Furthermore, ZINC000006036327 had lower skin irritancy and sensitization potential compared to OCA, also suggest the possibility of improved skin itching occurrence. ZINC000013374322 and ZINC000006036327 were found to be the best leading compounds to be FXR agonists. They are chosen as safe candidates for FXR target medicine, which play comparable pharmacological effects at lower doses.

Bile acid interactions with neurotransmitter transporters.

Synthesized in the liver from cholesterol, the bile acids (BAs) primary role is emulsifying fats to facilitate their absorption. BAs can cross the blood-brain barrier (BBB) and be synthesized in the brain. Recent evidence suggests a role for BAs in the gut-brain signaling by modulating the activity of various neuronal receptors and transporters, including the dopamine transporter (DAT). In this study, we investigated the effects of BAs and their relationship with substrates in three transporters of the solute carrier 6 family. The exposure to obeticholic acid (OCA), a semi-synthetic BA, elicits an inward current (IBA) in the DAT, the GABA transporter 1 (GAT1), and the glycine transporter 1 (GlyT1b); this current is proportional to the current generated by the substrate, respective to the transporter. Interestingly, a second consecutive OCA application to the transporter fails to elicit a response. The full displacement of BAs from the transporter occurs only after exposure to a saturating concentration of a substrate. In DAT, perfusion of secondary substrates norepinephrine (NE) and serotonin (5-HT) results in a second OCA current, decreased in amplitude and proportional to their affinity. Moreover, co-application of 5-HT or NE with OCA in DAT, and GABA with OCA in GAT1, did not alter the apparent affinity or the Imax, similar to what was previously reported in DAT in the presence of DA and OCA. The findings support the previous molecular model that suggested the ability of BAs to lock the transporter in an occluded conformation. The physiological significance is that it could possibly avoid the accumulation of small depolarizations in the cells expressing the neurotransmitter transporter. This achieves better transport efficiency in the presence of a saturating concentration of the neurotransmitter and enhances the action of the neurotransmitter on their receptors when they are present at reduced concentrations due to decreased availability of transporters.

Selected Aspects of the Intricate Background of Immune-Related Cholangiopathies-A Critical Overview.

Primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC) are rare immune-related cholangiopathies with still poorly explained pathogenesis. Although triggers of chronic inflammation with subsequent fibrosis that affect cholangiocytes leading to obliteration of bile ducts and conversion to liver cirrhosis are unclear, both disorders are regarded to be multifactorial. Different factors can contribute to the development of hepatocellular injury in the course of progressive cholestasis, including (1) body accumulation of bile acids and their toxicity, (2) decreased food intake and nutrient absorption, (3) gut microbiota transformation, and (4) reorganized host metabolism. Growing evidence suggests that intestinal microbiome composition not only can be altered by liver dysfunction, but in turn, it actively impacts hepatic conditions. In this review, we highlight the role of key factors such as the gut-liver axis, intestinal barrier integrity, bile acid synthesis and circulation, and microbiome composition, which seem to be strongly related to PBC and PSC outcome. Emerging treatments and future therapeutic strategies are also presented.

Update on the Pharmacological Treatment of Primary Biliary Cholangitis.

Ursodeoxycholic acid (UDCA) is the first-line therapy used for the treatment of PBC. In recent years, new pharmacological agents have been proposed for PBC therapy to cure UDCA-non-responders. Obeticholic acid (OCA) is registered in many countries for PBC, and fibrates also seem to be effective in ameliorating biochemistry alteration and symptoms typical of PBC. Moreover, a variety of new agents, acting with different mechanisms of action, are under clinical evaluation for PBC treatment, including PPAR agonists, anti-NOX agents, immunomodulators, and mesenchymal stem cell transplantation. Since an insufficient amount of data is currently available about the effect of these novel approaches on robust clinical endpoints, such as transplant-free survival, their clinical approval needs to be supported by the consistent improvement of these parameters. The intensive research in this field will hopefully lead to a novel treatment landscape for PBC in the near future, with innovative therapies based on the combination of multiple agents acting on different pathogenetic mechanisms.

Obeticholic Acid Induces Hepatoxicity Via FXR in the NAFLD Mice.

Objective: Obeticholic acid (OCA), a potent farnesoid X receptor (FXR) agonist, is a promising drug for nonalcoholic fatty liver disease (NAFLD); however, it can cause liver injury, especially at high doses. Here, we investigated the role of FXR in the high-dose OCA-induced hepatoxicity in the condition of the NAFLD mouse model. Methods: Wild-type (WT) mice and FXR-/- mice were administered with over-dose OCA (0.40%) and high-dose OCA (0.16%), in a high-fat diet. RNA-seq on liver samples of mice fed with high-dose OCA was performed to dig out the prominent biological events contributing to hepatic fibrosis. Results: Over-dose OCA induced liver injury and shortened survival in WT mice, but not FXR-/- mice. High-dose OCA caused hepatic stellate cell activation and liver fibrosis in the presence of FXR. Furthermore, high-dose OCA induced cholesterol accumulation in livers via the upregulation of genes involved in cholesterol acquisition and downregulation of genes regulating cholesterol degradation in liver, leading to the production of interleukin -1ß and an FXR-mediated inflammatory response. Conclusion: The high-dose OCA induced FXR-dependent hepatic injury via cholesterol accumulation and interleukin -1ß pathway in the NAFLD mice.

Metabolomic Study of High-Fat Diet-Induced Obese (DIO) and DIO Plus CCl4-Induced NASH Mice and the Effect of Obeticholic Acid.

The pathophysiology of nonalcoholic fatty liver disease (NAFLD) is a complex process involving metabolic and inflammatory changes in livers and other organs, but the pathogenesis is still not well clarified. Two mouse models were established to study metabolic alteration of nonalcoholic fatty liver and nonalcoholic steatohepatitis, respectively. The concentrations of metabolites in serum, liver and intestine content were measured by the AbsoluteIDQ® p180 Kit (Biocrates Life Sciences, Innsbruck, Austria). Multivariate statistical methods, pathway analysis, enrichment analysis and correlation analysis were performed to analyze metabolomic data. The metabolic characteristics of liver, serum and intestine content could be distinctly distinguished from each group, indicating the occurrence of metabolic disturbance. Among them, metabolic alteration of liver and intestine content was more significant. Based on the metabolic data of liver, 19 differential metabolites were discovered between DIO and control, 12 between DIO-CCl4 and DIO, and 47 between DIO-CCl4 and normal. These metabolites were mainly associated with aminoacyl-tRNA biosynthesis, nitrogen metabolism, lipid metabolism, glyoxylate and dicarboxylate metabolism, and amino metabolism. Further study revealed that the intervention of obeticholic acid (OCA) could partly reverse the damage of CCl4. The correlation analysis of metabolite levels and clinical parameters showed that phosphatidylcholines were negatively associated with serum alanine aminotransferase, aspartate aminotransferase, NAFLD activity score, and fibrosis score, while lysophosphatidylcholines, sphingomyelins, amino acids, and acylcarnitines shared the reverse pattern. Our study investigated metabolic alteration among control, NAFLD model, and OCA treatment groups, providing preclinical information to understand the mechanism of NAFLD and amelioration of OCA.

A consensus integrated care pathway for patients with primary biliary cholangitis: a guideline-based approach to clinical care of patients.

INTRODUCTION: Primary biliary cholangitis (PBC) is an infrequent, immune-mediated cholestatic liver disease, which can lead to liver fibrosis, cirrhosis and complications of end-stage liver disease. The established goals of treatment of PBC are prevention of end-stage liver disease and amelioration of associated symptoms. The European Association for the Study of the Liver (EASL) management guidelines provide extensive recommendations on the diagnosis and management of PBC. AREAS COVERED: This article describes the development by expert consensus of a 'PBC Integrated Patient Care Pathway' to simplify and standardize the management of PBC for clinicians based on current practice. EXPERT OPINION: Guideline adoption is potentially poor in practice since most patients with PBC in the community are seen by general gastroenterologists or hepatologists without a special interest in autoimmune liver disease. The PBC Integrated Patient Care Pathway is a best practice tool for clinicians designed to complement the EASL Clinical Practice Guidelines for the diagnosis and management of PBC patients. It gives clinicians a practical decision tree of the key steps in PBC management, thereby providing a simplified framework and an opportunity for more uniform practice that supports the safe and timely adoption of varied models of care provision to patients with PBC.

Recent advances in the development of farnesoid X receptor agonists.

Farnesoid X receptors (FXRs) are nuclear hormone receptors expressed in high amounts in body tissues that participate in bilirubin metabolism including the liver, intestines, and kidneys. Bile acids (BAs) are the natural ligands of the FXRs. FXRs regulate the expression of the gene encoding for cholesterol 7 alpha-hydroxylase, which is the rate-limiting enzyme in BA synthesis. In addition, FXRs play a critical role in carbohydrate and lipid metabolism and regulation of insulin sensitivity. FXRs also modulate live growth and regeneration during liver injury. Preclinical studies have shown that FXR activation protects against cholestasis-induced liver injury. Moreover, FXR activation protects against fatty liver injury in animal models of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), and improved hyperlipidemia, glucose intolerance, and insulin sensitivity. Obeticholic acid (OCA), a 6α-ethyl derivative of the natural human BA chenodeoxycholic acid (CDCA) is the first-in-class selective FXR agonist that is ~100-fold more potent than CDCA. Preliminary human clinical trials have shown that OCA is safe and effective. In a phase II clinical trial, administration of OCA was well-tolerated, increased insulin sensitivity and reduced markers of liver inflammation and fibrosis in patients with type II diabetes mellitus and NAFLD. In two clinical trials of OCA in patients with primary biliary cirrhosis (PBC), a progressive cholestatic liver disease, OCA significantly reduced serum alkaline phosphatase (ALP) levels, an important disease marker that correlates well with clinical outcomes of patients with PBC. Together, these studies suggest that FXR agonists could potentially be used as therapeutic tools in patients suffering from nonalcoholic fatty and cholestatic liver diseases. Larger and Longer-term studies are currently ongoing.